/*
 * SNMP Package
 *
 * Copyright (C) 2002, Jonathan Sevy <jsevy@mcs.drexel.edu>
 *
 * This is free software. Redistribution and use in source and binary forms, with
 * or without modification, are permitted provided that the following conditions
 * are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice, this
 *     list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation 
 *     and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products 
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */


package snmp;

import java.io.*;
import java.math.*;
import java.net.*;
import java.util.*;


/**
*	The class SNMPv1CommunicationInterface defines methods for communicating with SNMP entities.
*	The approach is that from version 1 of SNMP, using no encryption of data. Communication occurs
*	via UDP, using port 161, the standard SNMP port.
*/

public class SNMPv1CommunicationInterface
{
	public static final int SNMP_PORT = 161;
	
	// largest size for datagram packet payload; based on
	// RFC 1157, need to handle messages of at least 484 bytes
	public static final int MAXSIZE = 512;
	
	private int version;
	private InetAddress hostAddress;
	private String community;
	DatagramSocket dSocket;
	
	public int requestID = 1;

	private int port;
			
	
	
	
	/**
	*	Construct a new communication object to communicate with the specified host using the
	*	given community name. The version setting should be either 0 (version 1) or 1 (version 2,
	*	a la RFC 1157).
	 * @throws SocketException 
	*/
	
	public SNMPv1CommunicationInterface(int version, InetAddress hostAddress, String community) throws SocketException{
		this(version, hostAddress, SNMP_PORT,  community);
	}
	public SNMPv1CommunicationInterface(int version, InetAddress hostAddress, int port, String community)
		throws SocketException
	{
		this.version = version;
		this.hostAddress = hostAddress;
		this.port = port;
		this.community = community;
		try{
			dSocket = new DatagramSocket();
		}catch(java.net.BindException e){
			System.out.println("java.net.BindException:"+this.port);
			e.printStackTrace();
			dSocket = new DatagramSocket();
		}
		dSocket.setSoTimeout(15000);	//15 seconds
	}
	
	
	
	
	/**
	*	Permits setting timeout value for underlying datagram socket (in milliseconds).
	*/
	
	public void setSocketTimeout(int socketTimeout)
		throws SocketException
	{
		dSocket.setSoTimeout(socketTimeout);
	}
	
	
	
	/**
	*	Close the "connection" with the devive.
	*/
	
	public void closeConnection()
		throws SocketException
	{
		dSocket.close();
	}

	
	
	
	
	
	/**
	*	Retrieve all MIB variable values subsequent to the starting object identifier
	*	given in startID (in dotted-integer notation). Return as SNMPVarBindList object.
	*	Uses SNMPGetNextRequests to retrieve variable values in sequence.
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*/
	
	public SNMPVarBindList retrieveAllMIBInfo(String startID)
		throws IOException, SNMPBadValueException
	{
		// send GetNextRequests until receive
		// an error message or a repeat of the object identifier we sent out
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(startID);
		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
		SNMPSequence varList = new SNMPSequence();
		varList.addSNMPObject(nextPair);
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		byte[] messageEncoding = message.getBEREncoding();
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		
		dSocket.send(outPacket);
		
		
		
		while (errorStatus == 0)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
		
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			//errorStatus = ((BigInteger)((SNMPInteger)((receivedMessage.getPDU()).getSNMPObjectAt(1))).getValue()).intValue();
			
			
			varList = (receivedMessage.getPDU()).getVarBindList();
			SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
			
			SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
			SNMPObject newValue = newPair.getSNMPObjectAt(1);
			
			retrievedVars.addSNMPObject(newPair);
			
			
			if (requestedObjectIdentifier.equals(newObjectIdentifier))
				break;
				
			requestedObjectIdentifier = newObjectIdentifier;
		
			requestID++;
			pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
			message = new SNMPMessage(version, community, pdu);
			messageEncoding = message.getBEREncoding();
			outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
			
			dSocket.send(outPacket);
			
		}
			
		
		return retrievedVars;
		
	}
	
	
	
	private String hexByte(byte b)
	{
		int pos = b;
		if (pos < 0)
			pos += 256;
		String returnString = new String();
		returnString += Integer.toHexString(pos/16);
		returnString += Integer.toHexString(pos%16);
		return returnString;
	}
	
	
	
	
	
	/**
	*	Retrieve the MIB variable value corresponding to the object identifier
	*	given in itemID (in dotted-integer notation). Return as SNMPVarBindList object; if no
	*	such variable (either due to device not supporting it, or community name having incorrect
	*	access privilege), SNMPGetException thrown
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*   @throws SNMPGetException Thrown if supplied OID has value that can't be retrieved
	*/
	
	public SNMPVarBindList getMIBEntry(String itemID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetRequest to specified host to retrieve specified object identifier
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID);
		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
		SNMPSequence varList = new SNMPSequence();
		varList.addSNMPObject(nextPair);
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETREQUEST, requestID, errorStatus, errorIndex, varList);
		
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		
		byte[] messageEncoding = message.getBEREncoding();
		
		
		/*
		System.out.println("Request Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
			System.out.print(hexByte(messageEncoding[i]) + " ");
		*/
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for requestID & OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print(hexByte(encodedMessage[i]) + " ");
			}
			*/
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
					throw new SNMPGetException("OID " + itemID + " not available for retrieval", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());		
				
				
				varList = receivedPDU.getVarBindList();
				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
				
				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
				SNMPObject newValue = newPair.getSNMPObjectAt(1);
				
				// check the object identifier to make sure the correct variable has been received;
				// if not, just continue waiting for receive
				if (newObjectIdentifier.toString().equals(itemID))
				{
					// got the right one; add it to retrieved var list and break!
					retrievedVars.addSNMPObject(newPair);
					break;
				}
			
			}
			
		}
		
		
		requestID++;
		
		
		return retrievedVars;
		
	}
	
	
	
	
	/**
	*	Retrieve the MIB variable values corresponding to the object identifiers
	*	given in the array itemID (in dotted-integer notation). Return as SNMPVarBindList object; 
	*	if no such variable (either due to device not supporting it, or community name having incorrect
	*	access privilege), SNMPGetException thrown
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*   @throws SNMPGetException Thrown if one of supplied OIDs has value that can't be retrieved
	*/
	
	public SNMPVarBindList getMIBEntry(String[] itemID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetRequest to specified host to retrieve values of specified object identifiers
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		SNMPSequence varList = new SNMPSequence();
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		for (int i = 0; i < itemID.length; i++)
		{
    		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID[i]);
    		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
    		varList.addSNMPObject(nextPair);
		}
		
		
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETREQUEST, requestID, errorStatus, errorIndex, varList);
		
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		
		byte[] messageEncoding = message.getBEREncoding();
		
		
		/*
		System.out.println("Request Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
			System.out.print(hexByte(messageEncoding[i]) + " ");
		*/
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for requestID & OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print(hexByte(encodedMessage[i]) + " ");
			}
			*/
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
				{
					// determine error index
					errorIndex = receivedPDU.getErrorIndex();
					throw new SNMPGetException("OID " + itemID[errorIndex - 1] + " not available for retrieval", errorIndex, receivedPDU.getErrorStatus());		
				}
				
				// copy info from retrieved sequence to var bind list
				varList = receivedPDU.getVarBindList();
				
				for (int i = 0; i < varList.size(); i++)
        		{
    				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(i));
    				
    				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
    				SNMPObject newValue = newPair.getSNMPObjectAt(1);
    				
    				if (newObjectIdentifier.toString().equals(itemID[i]))
    				{
    				    retrievedVars.addSNMPObject(newPair);
    				}
    				else
    				{
    					// wrong OID; throw GetException
    					throw new SNMPGetException("OID " + itemID[i] + " expected at index " + i + ", OID " + newObjectIdentifier + " received", i+1, SNMPRequestException.FAILED);
    				}
				}
				
				break;
			
			}
			
		}
		
		
		requestID++;
		
		
		return retrievedVars;
		
	}
	
	
	
	
	
	/**
	*	Retrieve the MIB variable value corresponding to the object identifier following that
	*	given in itemID (in dotted-integer notation). Return as SNMPVarBindList object; if no
	*	such variable (either due to device not supporting it, or community name having incorrect
	*	access privilege), variable value will be SNMPNull object
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*   @throws SNMPGetException Thrown if one the OID following the supplied OID has value that can't be retrieved
	*/
	
	public SNMPVarBindList getNextMIBEntry(String itemID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetRequest to specified host to retrieve specified object identifier
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID);
		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
		SNMPSequence varList = new SNMPSequence();
		varList.addSNMPObject(nextPair);
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
		
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		
		byte[] messageEncoding = message.getBEREncoding();
		
		
		/*
		System.out.println("Request Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
			System.out.print(hexByte(messageEncoding[i]) + " ");
		*/
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for requestID & OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print(hexByte(encodedMessage[i]) + " ");
			}
			*/
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
					throw new SNMPGetException("OID " + itemID + " not available for retrieval", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());		
				
				
				varList = receivedPDU.getVarBindList();
				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
				
				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
				SNMPObject newValue = newPair.getSNMPObjectAt(1);
				
				retrievedVars.addSNMPObject(newPair);
				
				break;
			
			}
			
		}
		
		
		requestID++;
		
		
		return retrievedVars;
		
	}
	
	
	
	
	
	/**
	*	Retrieve the MIB variable value corresponding to the object identifiers following those
	*	given in the itemID array (in dotted-integer notation). Return as SNMPVarBindList object; 
	*	if no such variable (either due to device not supporting it, or community name having 
	*	incorrect access privilege), SNMPGetException thrown
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*   @throws SNMPGetException Thrown if OID following one of supplied OIDs has value that can't be retrieved
	*/
	
	public SNMPVarBindList getNextMIBEntry(String[] itemID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetRequest to specified host to retrieve values of specified object identifiers
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		SNMPSequence varList = new SNMPSequence();
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		for (int i = 0; i < itemID.length; i++)
		{
    		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID[i]);
    		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
    		varList.addSNMPObject(nextPair);
		}
		
	    SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		
		byte[] messageEncoding = message.getBEREncoding();
		
		
		/*
		System.out.println("Request Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
			System.out.print(hexByte(messageEncoding[i]) + " ");
		*/
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for requestID & OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print(hexByte(encodedMessage[i]) + " ");
			}
			*/
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
				{
					// determine error index
					errorIndex = receivedPDU.getErrorIndex();
					throw new SNMPGetException("OID following " + itemID[errorIndex - 1] + " not available for retrieval", errorIndex, receivedPDU.getErrorStatus());		
				}
				
				// copy info from retrieved sequence to var bind list
				varList = receivedPDU.getVarBindList();
				
				for (int i = 0; i < varList.size(); i++)
        		{
    				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(i));
    				
    				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
    				SNMPObject newValue = newPair.getSNMPObjectAt(1);
    				
    				retrievedVars.addSNMPObject(newPair);
    				
				}
				
				break;
			
			}
			
		}
		
		
		requestID++;
		
		
		return retrievedVars;
		
	}
	
	
	
	
	
	
	
	/**
	*	Set the MIB variable value of the object identifier
	*	given in startID (in dotted-integer notation). Return SNMPVarBindList object returned
	*	by device in its response; can be used to check that setting was successful.
	*	Uses SNMPGetNextRequests to retrieve variable values in sequence.
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*/
	
	public SNMPVarBindList setMIBEntry(String itemID, SNMPObject newValue)
		throws IOException, SNMPBadValueException, SNMPSetException
	{
		// send SetRequest to specified host to set value of specified object identifier
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID);
		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, newValue);
		
			
		
		SNMPSequence varList = new SNMPSequence();
		varList.addSNMPObject(nextPair);
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPSETREQUEST, requestID, errorStatus, errorIndex, varList);
		
		
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		byte[] messageEncoding = message.getBEREncoding();
		
		/*
		System.out.println("Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
		{
			System.out.print(getHex(messageEncoding[i]) + " ");
		}
		*/
		
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for correct OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print((encodedMessage[i]) + " ");
			}
			*/
		
		
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
				{
					switch (receivedPDU.getErrorStatus())
					{
						case 1:
							throw new SNMPSetException("Value supplied for OID " + itemID + " too big.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
						
						case 2:
							throw new SNMPSetException("OID " + itemID + " not available for setting.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
						
						case 3:
							throw new SNMPSetException("Bad value supplied for OID " + itemID + ".", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
							
						case 4:
							throw new SNMPSetException("OID " + itemID + " read-only.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
							
						default:
							throw new SNMPSetException("Error setting OID " + itemID + ".", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());	
							
					}
				}
				
				
				varList = receivedPDU.getVarBindList();
				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
				
				// check the object identifier to make sure the correct variable has been received;
				// if not, just continue waiting for receive
				if (((SNMPObjectIdentifier)newPair.getSNMPObjectAt(0)).toString().equals(itemID))
				{
					// got the right one; add it to retrieved var list and break!
					retrievedVars.addSNMPObject(newPair);
					break;
				}
			
			}
			
		}
		
		
		requestID++;
	
		
		return retrievedVars;
		
	}
	
	
	
	
	/**
	*	Set the MIB variable values of the supplied object identifiers given in the 
	*	itemID array (in dotted-integer notation). Return SNMPVarBindList returned
	*	by device in its response; can be used to check that setting was successful.
	*	Uses SNMPGetNextRequests to retrieve variable values in sequence.
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*/
	
	public SNMPVarBindList setMIBEntry(String[] itemID, SNMPObject[] newValue)
		throws IOException, SNMPBadValueException, SNMPSetException
	{
		// check that OID and value arrays have same size
		if (itemID.length != newValue.length)
		{
		    throw new SNMPSetException("OID and value arrays must have same size", 0, SNMPRequestException.FAILED);
		}
		
		
		// send SetRequest to specified host to set values of specified object identifiers
		
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		SNMPSequence varList = new SNMPSequence();
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		
		for (int i = 0; i < itemID.length; i++)
		{
    		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID[i]);
    		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, newValue[i]);
    		varList.addSNMPObject(nextPair);
		}
		
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPSETREQUEST, requestID, errorStatus, errorIndex, varList);
		SNMPMessage message = new SNMPMessage(version, community, pdu);
		
		byte[] messageEncoding = message.getBEREncoding();
		
		/*
		System.out.println("Message bytes:");
		
		for (int i = 0; i < messageEncoding.length; ++i)
		{
			System.out.print(getHex(messageEncoding[i]) + " ");
		}
		*/
		
		
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
		
		dSocket.send(outPacket);
		
		
		while (true)	// wait until receive reply for correct OID (or error)
		{
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			/*
			System.out.println("Message bytes:");
			
			for (int i = 0; i < encodedMessage.length; ++i)
			{
				System.out.print((encodedMessage[i]) + " ");
			}
			*/
		
		
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, throw SNMPGetException
				if (receivedPDU.getErrorStatus() != 0)
				{
					errorIndex = receivedPDU.getErrorIndex();
					
					switch (receivedPDU.getErrorStatus())
					{
						case 1:
							throw new SNMPSetException("Value supplied for OID " + itemID[errorIndex - 1] + " too big.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
						
						case 2:
							throw new SNMPSetException("OID " + itemID[errorIndex - 1] + " not available for setting.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
						
						case 3:
							throw new SNMPSetException("Bad value supplied for OID " + itemID[errorIndex - 1] + ".", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
							
						case 4:
							throw new SNMPSetException("OID " + itemID[errorIndex - 1] + " read-only.", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
							
						default:
							throw new SNMPSetException("Error setting OID " + itemID[errorIndex - 1] + ".", receivedPDU.getErrorIndex(), receivedPDU.getErrorStatus());
							
					}
				}
				
				
				// copy info from retrieved sequence to var bind list
				varList = receivedPDU.getVarBindList();
				
				for (int i = 0; i < varList.size(); i++)
        		{
    				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(i));
    				
    				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
    				//SNMPObject receivedValue = newPair.getSNMPObjectAt(1);
    				
    				if (newObjectIdentifier.toString().equals(itemID[i]))
    				{
    				    retrievedVars.addSNMPObject(newPair);
    				}
    				else
    				{
    					// wrong OID; throw GetException
    					throw new SNMPSetException("OID " + itemID[i] + " expected at index " + i + ", OID " + newObjectIdentifier + " received", i+1, SNMPRequestException.FAILED);
    				}
				}
				
				break;
			
			}
			
		}
		
		
		requestID++;
	
		
		return retrievedVars;
		
	}
	
	
	
	
	/**
	*	Retrieve all MIB variable values whose OIDs start with the supplied baseID. Since the entries of
	*   an SNMP table have the form  <baseID>.<tableEntry>.<index>, this will retrieve all of the table 
	*   data as an SNMPVarBindList object consisting of sequence of SNMPVariablePairs.
	*	Uses SNMPGetNextRequests to retrieve variable values in sequence.
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*/
	
	public SNMPVarBindList retrieveMIBTable(String baseID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetNextRequests until receive
		// an error message or a repeat of the object identifier we sent out
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		String currentID = baseID;
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(currentID);
		
		
		while (errorStatus == 0)
		{
			
			SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
        	SNMPSequence varList = new SNMPSequence();
        	varList.addSNMPObject(nextPair);
        	SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
        	SNMPMessage message = new SNMPMessage(version, community, pdu);
        	byte[] messageEncoding = message.getBEREncoding();
        	DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
        	
        	/*
    		System.out.println("Request bytes:");
    		
    		for (int i = 0; i < messageEncoding.length; ++i)
    		{
    			System.out.print(getHex(messageEncoding[i]) + " ");
    		}
    		*/
    		
        	dSocket.send(outPacket);
        	
        	
    		DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
		
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem, just break - could be there are no additional OIDs
				if (receivedPDU.getErrorStatus() != 0)
				{
					break;
					//throw new SNMPGetException("OID following " + requestedObjectIdentifier + " not available for retrieval");		
				}
				
				varList = receivedPDU.getVarBindList();
				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
				
				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
				SNMPObject newValue = newPair.getSNMPObjectAt(1);
				
				// now see if retrieved ID starts with table base; if not, done with table - break
    			String newOIDString = (String)newObjectIdentifier.toString();
    			if (!newOIDString.startsWith(baseID))
    				break;
    			
    			retrievedVars.addSNMPObject(newPair);
    				
    			requestedObjectIdentifier = newObjectIdentifier;
    		
    			requestID++;
			
			}
			
			
		}
			
		
		return retrievedVars;
		
	}
	
	
	
	
	/**
	*	Retrieve all MIB variable values whose OIDs start with the supplied baseIDs. The normal way for
	*   this to be used is for the base OID array to consist of the base OIDs of the columns of a table.
	*   This method will then retrieve all of the entries of the table corresponding to these columns, one 
	*   row at a time (i.e., the entries for each row will be retrieved in a single SNMP request). This 
	*   will retrieve the table data as an SNMPVarBindList object consisting of sequence of SNMPVariablePairs,
	*   with the entries for each row grouped together. This may provide a more convenient arrangement of
	*   the table data than the simpler retrieveMIBTable method taking a single OID as argument; in addition,
	*   it's more efficient, requiring one SNMP request per row rather than one request per entry.
	*	Uses SNMPGetNextRequests to retrieve variable values for each row in sequence.
	*	@throws IOException Thrown when timeout experienced while waiting for response to request.
	*	@throws SNMPBadValueException 
	*   @throws SNMPGetException Thrown if incomplete row retrieved
	*/
	
	public SNMPVarBindList retrieveMIBTable(String[] baseID)
		throws IOException, SNMPBadValueException, SNMPGetException
	{
		// send GetNextRequests until receive
		// an error message or a repeat of the object identifier we sent out
		SNMPVarBindList retrievedVars = new SNMPVarBindList();
		
		int errorStatus = 0;
		int errorIndex = 0;
		
		SNMPObjectIdentifier[] requestedObjectIdentifier = new SNMPObjectIdentifier[baseID.length];
		for (int i = 0; i < baseID.length; i++)
    	{
       		requestedObjectIdentifier[i] = new SNMPObjectIdentifier(baseID[i]);
    	}
    	

retrievalLoop:
		
		while (errorStatus == 0)
		{
			
			SNMPSequence varList = new SNMPSequence();
        	
        	for (int i = 0; i < requestedObjectIdentifier.length; i++)
    		{
        		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier[i], new SNMPInteger(0));
        		varList.addSNMPObject(nextPair);
    		}
    		
    	    SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETNEXTREQUEST, requestID, errorStatus, errorIndex, varList);
    		SNMPMessage message = new SNMPMessage(version, community, pdu);
    		
    		byte[] messageEncoding = message.getBEREncoding();
    		
        	DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, this.port);
        	
        	/*
    		System.out.println("Request bytes:");
    		
    		for (int i = 0; i < messageEncoding.length; ++i)
    		{
    			System.out.print(getHex(messageEncoding[i]) + " ");
    		}
    		*/
    		
        	dSocket.send(outPacket);
        	
        	
    		DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
		
			dSocket.receive(inPacket);
			
			byte[] encodedMessage = inPacket.getData();
			
			
			SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
			SNMPPDU receivedPDU = receivedMessage.getPDU();
			
			// check request identifier; if incorrect, just ignore packet and continue waiting
			if (receivedPDU.getRequestID() == requestID)
			{
				
				// check error status; if retrieval problem for error index 1, just break - assume there are no additional OIDs
				// to retrieve. If index is other than 1, throw exception
				if (receivedPDU.getErrorStatus() != 0)
				{
					int retrievedErrorIndex = receivedPDU.getErrorIndex();
					
					if (retrievedErrorIndex == 1)
					{
					    break retrievalLoop;
					}
					else
					{
					    throw new SNMPGetException("OID following " + requestedObjectIdentifier[retrievedErrorIndex - 1] + " not available for retrieval", retrievedErrorIndex, receivedPDU.getErrorStatus());
					}	
				}
				
				// copy info from retrieved sequence to var bind list
				varList = receivedPDU.getVarBindList();
				
				// make sure got the right number of vars in reply; if not, throw GetException
				if(varList.size() != requestedObjectIdentifier.length)
				{
				    throw new SNMPGetException("Incomplete row of table received", 0, SNMPRequestException.FAILED);
				}
				
				// copy the retrieved variable pairs into retrievedVars
				for (int i = 0; i < varList.size(); i++)
        		{
    				SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(i));
    				
    				SNMPObjectIdentifier newObjectIdentifier = (SNMPObjectIdentifier)(newPair.getSNMPObjectAt(0));
    				SNMPObject newValue = newPair.getSNMPObjectAt(1);
    				
    				// now see if retrieved ID starts with table base; if not, done with table - break
        			String newOIDString = (String)newObjectIdentifier.toString();
        			if (!newOIDString.startsWith(baseID[i]))
        			{
            			if (i == 0)
            			{
            				// it's the first element of the row; just break
            				break retrievalLoop;
            			}
            			else
            			{
            			    // it's a subsequent row element; throw exception
            			    throw new SNMPGetException("Incomplete row of table received", i+1, SNMPRequestException.FAILED);
            			}
        			}
        				
        			retrievedVars.addSNMPObject(newPair);
    				
    				// set requested identifiers array to current identifiers to do get-next for next row
    			    requestedObjectIdentifier[i] = newObjectIdentifier;
				}
				
    			
    			requestID++;
			
			}
			
			
		}
			
		
		return retrievedVars;
		
	}
	
	
	
	/*
	public void broadcastDiscovery(String itemID)
		throws IOException, SNMPBadValueException
	{
		// send GetRequest to all hosts to retrieve specified object identifier
		
	
		int errorStatus = 0;
		int errorIndex = 0;
		
		int requestID = 0;
		SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID);
		SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
		SNMPSequence varList = new SNMPSequence();
		varList.addSNMPObject(nextPair);
		SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETREQUEST, requestID, errorStatus, errorIndex, varList);
		SNMPMessage message = new SNMPMessage(0, community, pdu);
		byte[] messageEncoding = message.getBEREncoding();
		DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, SNMPPORT);
		
		
		dSocket.send(outPacket);
		
		
		
	}
	
	
	
	
	public String receiveDiscovery()
		throws IOException, SNMPBadValueException
	{
		// receive responses from hosts responding to discovery message
		
		int MAXSIZE = 512;
			
		String returnString = new String();
		
		int errorStatus = 0;
		int errorIndex = 0;
		int requestID = 0;
		
		
		DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
		
		dSocket.receive(inPacket);
		String hostString = inPacket.getAddress().toString();
		returnString += "Packet received from: " + hostString + "\n";
		
		byte[] encodedMessage = inPacket.getData();
		
		
		returnString += "Message bytes:" + "\n";
		
		for (int i = 0; i < encodedMessage.length; ++i)
		{
			returnString += (encodedMessage[i]) + " ";
		}
		
		
		SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
		SNMPSequence varList = (receivedMessage.getPDU()).getVarBindList();
		SNMPSequence newPair = (SNMPSequence)(varList.getSNMPObjectAt(0));
		SNMPObject newValue = newPair.getSNMPObjectAt(1);
		
		// return just value string
		returnString += newValue.toString() + "\n\n";
		
		
		
		returnString += "Received message contents:\n";
		returnString += receivedMessage.toString() + "\n";
		System.out.println(receivedMessage.toString());
		
	
		
		return returnString;
		
	}
	
	
	
	
	public String discoverDevices(String itemID)
		throws IOException, SNMPBadValueException
	{
		// send GetRequest to all hosts to retrieve specified object identifier
		
		int MAXSIZE = 512;
		
			
		String returnString = new String();
		
		try
		{
			int errorStatus = 0;
			int errorIndex = 0;
			
			DatagramSocket dSocket = new DatagramSocket();
			
			int requestID = 0;
			SNMPObjectIdentifier requestedObjectIdentifier = new SNMPObjectIdentifier(itemID);
			SNMPVariablePair nextPair = new SNMPVariablePair(requestedObjectIdentifier, new SNMPInteger(0));
			SNMPSequence varList = new SNMPSequence();
			varList.addSNMPObject(nextPair);
			SNMPPDU pdu = new SNMPPDU(SNMPBERCodec.SNMPGETREQUEST, requestID, errorStatus, errorIndex, varList);
			SNMPMessage message = new SNMPMessage(0, community, pdu);
			byte[] messageEncoding = message.getBEREncoding();
			DatagramPacket outPacket = new DatagramPacket(messageEncoding, messageEncoding.length, hostAddress, SNMPPORT);
			
			
			dSocket.send(outPacket);
			
			
			DatagramPacket inPacket = new DatagramPacket(new byte[MAXSIZE], MAXSIZE);
			
			while (true)
			{
				dSocket.receive(inPacket);
				String hostString = inPacket.getAddress().toString();
				returnString += "Packet received from: " + hostString + "\n";
				
				byte[] encodedMessage = inPacket.getData();
				
				
				returnString += "Message bytes:" + "\n";
				
				for (int i = 0; i < encodedMessage.length; ++i)
				{
					returnString += (encodedMessage[i]) + " ";
				}
				
				
				SNMPMessage receivedMessage = new SNMPMessage(SNMPBERCodec.extractNextTLV(encodedMessage,0).value);
				returnString += "Received message contents:\n";
				returnString += receivedMessage.toString() + "\n";
				
	
			}
		}
		catch (Exception e)
		{
		
		}
		
		return returnString;
		
	}
	
	
	
	private String getHex(byte theByte)
	{
		int b = theByte;
		
		if (b < 0)
			b += 256;
		
		String returnString = new String(Integer.toHexString(b));
		
		// add leading 0 if needed
		if (returnString.length()%2 == 1)
			returnString = "0" + returnString;
			
		return returnString;
	}
	
	*/
	
	
	
}